<!DOCTYPE html>
<html>
  <body onload="loaded()">
    <span style="position: relative; top: 100px">foo<br>
      <span id="ins-point">bar</span></span>
    <script>
      function loaded() {
        var insPoint = document.getElementById("ins-point");
        var span = document.createElement("span");
        span.style.position = "absolute";
        span.style.top = 0;
        span.appendChild(document.createTextNode("abs"));
        insPoint.insertBefore(span, insPoint.firstChild);
      }
    </script>
  </body>
</html>
